/**
 * @file
 * @brief Generic doubly linked list
 * @note Modified from Linux source
 */

#ifndef _LIST_H
#define _LIST_H


struct list_head {
    struct list_head *next, *prev;
};

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) \
    struct list_head name = LIST_HEAD_INIT(name)

static inline void INIT_LIST_HEAD(struct list_head *list)
{
    list->next = list;
    list->prev = list;
}

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head *new,
        struct list_head *prev,
        struct list_head *next)
{
    next->prev = new;
    new->next = next;
    new->prev = prev;
    prev->next = new;
}

/**
 * @brief Add a new entry
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 *
 * @param new New entry to be added
 * @param head List head to add it after
 */
static inline void list_add(struct list_head *new, struct list_head *head)
{
    __list_add(new, head, head->next);
}


/**
 * @brief Add a new entry
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 *
 * @param new New entry to be added
 * @param head List head to add it before
 */
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
    __list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
    next->prev = prev;
    prev->next = next;
}

/**
 * @brief Deletes entry from list.
 * @note list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 * @param entry The element to delete from the list.
 */
static inline void list_del(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = (void *)0;
    entry->prev = (void *)0;
}

/**
 * @brief Replace old entry by new one
 *
 * If \c old was empty, it will be overwritten.
 *
 * @param old The element to be replaced
 * @param new The new element to insert
 */
static inline void list_replace(struct list_head *old,
        struct list_head *new)
{
    new->next = old->next;
    new->next->prev = new;
    new->prev = old->prev;
    new->prev->next = new;
}

static inline void list_replace_init(struct list_head *old,
        struct list_head *new)
{
    list_replace(old, new);
    INIT_LIST_HEAD(old);
}

/**
 * @brief Deletes entry from list and reinitialize it.
 * @param entry The element to delete from the list.
 */
static inline void list_del_init(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    INIT_LIST_HEAD(entry);
}

/**
 * @brief Delete from one list and add as another's head
 * @param list The entry to move
 * @param head The head that will precede our entry
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
    __list_del(list->prev, list->next);
    list_add(list, head);
}

/**
 * @brief Delete from one list and add as another's tail
 * @param list The entry to move
 * @param head The head that will follow our entry
 */
static inline void list_move_tail(struct list_head *list,
        struct list_head *head)
{
    __list_del(list->prev, list->next);
    list_add_tail(list, head);
}

/**
 * @brief Tests whether \c list is the last entry in list \c head
 * @param list The entry to test
 * @param head The head of the list
 */
static inline int list_is_last(const struct list_head *list,
        const struct list_head *head)
{
    return list->next == head;
}

/**
 * @brief Tests whether a list is empty
 * @param head The list to test.
 */
static inline int list_empty(const struct list_head *head)
{
    return head->next == head;
}

/**
 * @brief Rotate the list to the left
 * @param head The head of the list
 */
static inline void list_rotate_left(struct list_head *head)
{
    struct list_head *first;

    if (!list_empty(head)) {
        first = head->next;
        list_move_tail(first, head);
    }
}

/**
 * @brief Tests whether a list has just one entry.
 * @param head The list to test.
 */
static inline int list_is_singular(const struct list_head *head)
{
    return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head *list,
        struct list_head *head, struct list_head *entry)
{
    struct list_head *new_first = entry->next;
    list->next = head->next;
    list->next->prev = list;
    list->prev = entry;
    entry->next = list;
    head->next = new_first;
    new_first->prev = head;
}

/**
 * @brief Cut a list into two
 *
 * This helper moves the initial part of \c head, up to and
 * including \c entry, from \c head to \c list. You should
 * pass on \c entry an element you know is on \c head. \c list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 * @param list A new list to add all removed entries
 * @param head A list with entries
 * @param entry An entry within head, could be the head itself
 * and if so we won't cut the list
 */
static inline void list_cut_position(struct list_head *list,
        struct list_head *head, struct list_head *entry)
{
    if (list_empty(head))
        return;
    if (list_is_singular(head) &&
            (head->next != entry && head != entry))
        return;
    if (entry == head)
        INIT_LIST_HEAD(list);
    else
        __list_cut_position(list, head, entry);
}

static inline void __list_splice(const struct list_head *list,
        struct list_head *prev,
        struct list_head *next)
{
    struct list_head *first = list->next;
    struct list_head *last = list->prev;

    first->prev = prev;
    prev->next = first;

    last->next = next;
    next->prev = last;
}

/**
 * @brief Join two lists, this is designed for stacks
 * @param list The new list to add.
 * @param head The place to add it in the first list.
 */
static inline void list_splice(const struct list_head *list,
        struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head, head->next);
}

/**
 * @brief Join two lists, each list being a queue
 * @param list The new list to add.
 * @param head The place to add it in the first list.
 */
static inline void list_splice_tail(struct list_head *list,
        struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head->prev, head);
}

/**
 * @brief Join two lists and reinitialise the emptied list.
 *
 * The list at \c list is reinitialised
 *
 * @param list The new list to add.
 * @param head The place to add it in the first list.
 */
static inline void list_splice_init(struct list_head *list,
        struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head, head->next);
        INIT_LIST_HEAD(list);
    }
}

/**
 * @brief Join two lists and reinitialise the emptied list
 *
 * Each of the lists is a queue.
 * The list at \c list is reinitialised
 *
 * @param list The new list to add.
 * @param head The place to add it in the first list.
 */
static inline void list_splice_tail_init(struct list_head *list,
        struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head->prev, head);
        INIT_LIST_HEAD(list);
    }
}

#ifndef offsetof /* <stddef.h> has defined offsetof() */

#if __GNUC__ >= 4
#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
#endif

#ifdef __compiler_offsetof
#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
#else
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

#endif

/**
 * @brief Cast a member of a structure out to the containing structure
 * @param ptr The pointer to the member.
 * @param type The type of the container struct this is embedded in.
 * @param member The name of the member within the struct.
 */
#define container_of(ptr, type, member) ({			\
	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
	(type *)( (char *)__mptr - offsetof(type,member) );})

/**
 * @brief Get the struct for this entry
 * @param ptr The &struct list_head pointer.
 * @param type The type of the struct this is embedded in.
 * @param member The name of the list_struct within the struct.
 */
#define list_entry(ptr, type, member) \
    container_of(ptr, type, member)

/**
 * @brief Get the first element from a list
 * @note List is expected to be not empty.
 * @param ptr The list head to take the element from.
 * @param type The type of the struct this is embedded in.
 * @param member The name of the list_struct within the struct.
 */
#define list_first_entry(ptr, type, member) \
    list_entry((ptr)->next, type, member)

/**
 * @brief Iterate over a list
 * @param pos The &struct list_head to use as a loop cursor.
 * @param head The head for your list.
 */
#define list_for_each(pos, head) \
    for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * @brief Iterate over a list backwards
 * @param pos The &struct list_head to use as a loop cursor.
 * @param head The head for your list.
 */
#define list_for_each_prev(pos, head) \
    for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * @brief Iterate over a list safe against removal of list entry
 * @param pos The &struct list_head to use as a loop cursor.
 * @param n Another &struct list_head to use as temporary storage
 * @param head The head for your list.
 */
#define list_for_each_safe(pos, n, head) \
    for (pos = (head)->next, n = pos->next; pos != (head); \
            pos = n, n = pos->next)

/**
 * @brief Iterate over a list backwards safe against removal of list entry
 * @param pos The &struct list_head to use as a loop cursor.
 * @param n Another &struct list_head to use as temporary storage
 * @param head The head for your list.
 */
#define list_for_each_prev_safe(pos, n, head) \
    for (pos = (head)->prev, n = pos->prev; pos != (head); \
            pos = n, n = pos->prev)

/**
 * @brief Iterate over list of given type
 * @param pos The type * to use as a loop cursor.
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry(pos, head, member)				\
    for (pos = list_entry((head)->next, typeof(*pos), member); \
            &pos->member != (head); 	\
            pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * @brief Iterate backwards over list of given type.
 * @param pos The type * to use as a loop cursor.
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)			\
    for (pos = list_entry((head)->prev, typeof(*pos), member);	\
            &pos->member != (head); 	\
            pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * @brief Prepare a pos entry for use in list_for_each_entry_continue()
 *
 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
 *
 * @param pos The type * to use as a start point
 * @param head The head of the list
 * @param member The name of the list_struct within the struct.
 */
#define list_prepare_entry(pos, head, member) \
    ((pos) ? : list_entry(head, typeof(*pos), member))

/**
 * @brief Continue iteration over list of given type
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 *
 * @param pos The type * to use as a loop cursor.
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_continue(pos, head, member) 		\
    for (pos = list_entry(pos->member.next, typeof(*pos), member);	\
            &pos->member != (head);	\
            pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * @brief Iterate backwards from the given point
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 *
 * @param pos The type * to use as a loop cursor.
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)		\
    for (pos = list_entry(pos->member.prev, typeof(*pos), member);	\
            &pos->member != (head);	\
            pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * @brief Iterate over list of given type from the current point
 *
 * Iterate over list of given type, continuing from current position.
 * @param pos The type * to use as a loop cursor.
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_from(pos, head, member) 			\
    for (; &pos->member != (head);	\
            pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * @brief Iterate over list of given type safe against removal of list entry
 * @param pos The type * to use as a loop cursor.
 * @param n Another type * to use as temporary storage
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
    for (pos = list_entry((head)->next, typeof(*pos), member),	\
            n = list_entry(pos->member.next, typeof(*pos), member);	\
            &pos->member != (head); 					\
            pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * @brief Continue list iteration safe against removal
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 *
 * @param pos The type * to use as a loop cursor.
 * @param n Another type * to use as temporary storage
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member) 		\
    for (pos = list_entry(pos->member.next, typeof(*pos), member), 		\
            n = list_entry(pos->member.next, typeof(*pos), member);		\
            &pos->member != (head);						\
            pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * @brief Iterate over list from current point safe against removal
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 *
 * @param pos The type * to use as a loop cursor.
 * @param n Another type * to use as temporary storage
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_safe_from(pos, n, head, member) 			\
    for (n = list_entry(pos->member.next, typeof(*pos), member);		\
            &pos->member != (head);						\
            pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * @brief Iterate backwards over list safe against removal
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 *
 * @param pos The type * to use as a loop cursor.
 * @param n Another type * to use as temporary storage
 * @param head The head for your list.
 * @param member The name of the list_struct within the struct.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member)		\
    for (pos = list_entry((head)->prev, typeof(*pos), member),	\
            n = list_entry(pos->member.prev, typeof(*pos), member);	\
            &pos->member != (head); 					\
            pos = n, n = list_entry(n->member.prev, typeof(*n), member))

/**
 * @brief Reset a stale list_for_each_entry_safe loop
 *
 * list_safe_reset_next() is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next() is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 *
 * @param pos the loop cursor used in the list_for_each_entry_safe loop
 * @param n temporary storage used in list_for_each_entry_safe
 * @param member the name of the list_struct within the struct.
 */
#define list_safe_reset_next(pos, n, member)				\
    n = list_entry(pos->member.next, typeof(*pos), member)

#endif /* ! _LIST_H */
